A Fresh Look at Energy, Materials, and Labor in Agriculture

An understanding of agriculture's energy, material, and labor requirements is essential for achieving economic and ecological sustainability, and for assessing the effectiveness of relevant policy decisions (biofuel subsidies, regulations, labeling, etc.). Previous studies of energy, materials, and labor use in farming have been based on either unverified voluntary reporting or test plots, rather than on the high-resolution measurements of mass and energy flows. Here we present a recursive analysis of 1.25 million data points describing in unprecedented detail the resource transactions on a 60 ha farm functioning for over 6 years. This analysis highlights the importance of accounting for all types of materials, as well as capital equipment, non-field labor, and commuting. The superior energy efficiency of the farm's energy-saving methods, including green manure, crop rotation, composting, and short-duration grazing -- compared with conventional methods -- persists even when the higher labor requirements are taken into account. One of the farm's methods, however -- the use of horses for traction -- is shown to be highly inefficient compared with mechanical tractors

Barnett Shale in Texas: Promise and Problems

Estimates of Production from Barnett Shale by Tadeusz Patze

A Probabilistic Analysis of the Switchgrass Ethanol Cycle

The switchgrass-driven process for producing ethanol has received much popular attention. However, a realistic analysis of this process indicates three serious limitations: (a) If switchgrass planted on 140 million hectares (the entire area of active U.S. cropland) were used as feedstock and energy source for ethanol production, the net ethanol yield would replace on average about 20% of today’s gasoline consumption in the U.S. (b) Because nonrenewable resources are required to produce ethanol from switchgrass, the incremental gas emissions would be on average 55 million tons of equivalent carbon dioxide per year to replace just 10% of U.S. automotive gasoline. (c) In terms of delivering electrical or mechanical power, ethanol from 1 hectare (10,000 m2) of switchgrass is equivalent, on average, to 30 m2 of low-efficiency photovoltaic cells. This analysis suggests that investing toward more efficient and durable solar cells, and batteries, may be more promising than investing in a process to convert switchgrass to ethanol

A Probabilistic Analysis of the Switchgrass Ethanol Cycle

The switchgrass-driven process for producing ethanol has received much popular attention. However, a realistic analysis of this process indicates three serious limitations: (a) If switchgrass planted on 140 million hectares (the entire area of active U.S. cropland) were used as feedstock and energy source for ethanol production, the net ethanol yield would replace on average about 20% of today’s gasoline consumption in the U.S. (b) Because nonrenewable resources are required to produce ethanol from switchgrass, the incremental gas emissions would be on average 55 million tons of equivalent carbon dioxide per year to replace just 10% of U.S. automotive gasoline. (c) In terms of delivering electrical or mechanical power, ethanol from 1 hectare (10,000 m2) of switchgrass is equivalent, on average, to 30 m2 of low-efficiency photovoltaic cells. This analysis suggests that investing toward more efficient and durable solar cells, and batteries, may be more promising than investing in a process to convert switchgrass to ethanol.cellulose; yield; conservation law; GHG emissions; monte carlo

Evaluation of Rwanda’s Energy Resources

Energy flows in a fertile environment drive societal development and progress. To develop a country sustainably, striking balance between environmental management, natural resource use, and energy generation is a must. However, developing a country with limited access to energy and critical levels of environmental depletion is challenging. This description fits Rwanda, which faces a dual crisis of energy supply shortages and environment depletion. Overpopulation is driving urban and agricultural expansion which in turn unbalance biomass demand to supply the growing energy needs and exacerbate environmental damage. Just when urgent actions must be taken to overcome this current debacle, political aspirations seek to turn Rwanda into a middle- and subsequently high-income country. From our analysis, the available energy resources can only maintain current population in Rwanda as a low-income country. To become an average middle-income country, Rwanda needs an equivalent of 3 Mtoe /yr (≈20 Mbbl /yr) of oil imports, and must install a nominal capacity of 90 GW of solar photovoltaics (PV). For a high-income country, it is necessary to obtain an extra power input of 11.4Mtoe /yr (≈77 Mbbl /yr) of oil imports and to install a nominal capacity of 400 GW of solar PV. Comparing current power generation capacity in Rwanda against the extra power needed to achieve the middle-income and high-income status indicates a mismatch between available resources and developmental goals

Evaluation of Rwanda’s Energy Resources

Energy flows in a fertile environment drive societal development and progress. To develop a country sustainably, striking balance between environmental management, natural resource use, and energy generation is a must. However, developing a country with limited access to energy and critical levels of environmental depletion is challenging. This description fits Rwanda, which faces a dual crisis of energy supply shortages and environment depletion. Overpopulation is driving urban and agricultural expansion which in turn unbalance biomass demand to supply the growing energy needs and exacerbate environmental damage. Just when urgent actions must be taken to overcome this current debacle, political aspirations seek to turn Rwanda into a middle- and subsequently high-income country. From our analysis, the available energy resources can only maintain current population in Rwanda as a low-income country. To become an average middle-income country, Rwanda needs an equivalent of 3 Mtoe /yr (≈20 Mbbl /yr) of oil imports, and must install a nominal capacity of 90 GW of solar photovoltaics (PV). For a high-income country, it is necessary to obtain an extra power input of 11.4Mtoe /yr (≈77 Mbbl /yr) of oil imports and to install a nominal capacity of 400 GW of solar PV. Comparing current power generation capacity in Rwanda against the extra power needed to achieve the middle-income and high-income status indicates a mismatch between available resources and developmental goals